Dear fellow huber sounds to me like fungus.Their is a product out on the market called Methylene Blue made by kordon that may be of use. Back in the day when I had my pet store I had a lot of customers who raised angel fish that would buy and use this product with great success. Again I am certain you have a problem whith fungus probally the parrents of these eggs are new to breeding. Somtimes it takes several attempts for angel fish that have recently paired up to learn how to take care of their eggs.Ask your self do these angel fish stay gaurd over their eggs ? Do they take turns fanning their eggs with their mouths more experienced angle fish will remove fungus infected eggs so the fungus wont spread. If they are not good parrents try to seperate the eggs from the parrents and put a air stone below the eggs for airation along with the a fore said product.This will increase the odds of success for the eggs to hatch.Also if left un checked likely all the eggs will be infected.